B-cell-activating Factor Belonging To The TNF Family Research Articles

Belimumab in the treatment of systemic lupus erythematosus: 20 years of basic research, 10 years of clinical practice

Currently, strong evidence has been obtained for the fundamental role of pathological activation of B cells in the pathogenesis of immunoinflammatory (autoimmune) rheumatic diseases (IMRD), and drugs that specifically modulate the function or cause depletion of various subpopulations of B cells and plasma cells are considered a promising direction. pharmacotherapy of these diseases. of particular interest is belimumab (BLM), a human monoclonal antibody (mAb) (IgG1λ) to BAFF (B cell-activating factor belonging to the TNF family), which is the first “targeted” biological drug specially developed for the treatment of systemic lupus erythematosus (SLE). The efficacy and safety of BLM in SLE in adults and children, including lupus nephritis, in combination therapy with rituximab, steroid-sparing effect, the ability to prevent irreversible damage to internal organs dictate the need for its wider application in clinical practice.

Differences in Tfh Cell Response between the Graft and Spleen with Chronic Allograft Nephropathy

The aim of this study was to investigate follicular helper T (Tfh) cell response and its difference between renal graft and spleen in a rat renal transplantation model undergoing chronic allograft nephropathy (CAN). Orthotopical kidney transplantations were performed on Fischer (F344) rats and transplanted to Lewis rats, using syngeneic Lewis–Lewis grafts as controls. Tissue samples were collected at 8 weeks posttransplantation. The status of Tfh cell response was assessed by measuring the levels of transcription factor B-cell lymphoma 6 (Bcl-6), interleukin-21 (IL-21), chemokine receptor type 5 (CXCR5), and B-cell-activating factor belonging to the TNF family (BAFF). Tfh cell response was upregulated in both renal graft and spleen of the CAN group compared to the control group. However, Tfh cell response of the spleen was weaker than that of the graft, which was possibly related to the upregulation of splenic Treg activation. Also, the difference between two tissues was partially associated with the different expressions of tristetraprolin (TTP)/IL-10. Our data help improve our understanding of the role of Tfh cell response in the body with CAN and may provide a valuable clue for better treatment of CAN.

A mutation in caspase-9 decreases the expression of BAFFR and ICOS in patients with immunodeficiency and lymphoproliferation.

Lymphocyte apoptosis is mainly induced by either death receptor-dependent activation of caspase-8 or mitochondria-dependent activation of caspase-9. Mutations in caspase-8 lead to autoimmunity/lymphoproliferation and immunodeficiency. This work describes a heterozygous H237P mutation in caspase-9 that can lead to similar disorders. H237P mutation was detected in two patients: Pt1 with autoimmunity/lymphoproliferation, severe hypogammaglobulinemia and Pt2 with mild hypogammaglobulinemia and Burkitt lymphoma. Their lymphocytes displayed defective caspase-9 activity and decreased apoptotic and activation responses. Transfection experiments showed that mutant caspase-9 display defective enzyme and proapoptotic activities and a dominant-negative effect on wild-type caspase-9. Ex vivo analysis of the patients' lymphocytes and in vitro transfection experiments showed that the expression of mutant caspase-9 correlated with a downregulation of BAFFR (B-cell-activating factor belonging to the TNF family (BAFF) receptor) in B cells and ICOS (inducible T-cell costimulator) in T cells. Both patients carried a second inherited heterozygous mutation missing in the relatives carrying H237P: Pt1 in the transmembrane activator and CAML interactor (TACI) gene (S144X) and Pt2 in the perforin (PRF1) gene (N252S). Both mutations have been previously associated with immunodeficiencies in homozygosis or compound heterozygosis. Taken together, these data suggest that caspase-9 mutations may predispose to immunodeficiency by cooperating with other genetic factors, possibly by downregulating the expression of BAFFR and ICOS.

HIV-1 gp41 envelope IgA is frequently elicited after transmission but has an initial short response half-life.

Prevention of HIV-1 transmission at mucosal surfaces will likely require durable pre-existing mucosal anti-HIV-1 antibodies (Abs). Defining the ontogeny, specificities and potentially protective nature of the initial mucosal virus-specific B-cell response will be critical for understanding how to induce protective Ab responses by vaccination. Genital fluids from patients within the earliest stages of acute HIV-1 infection (Fiebig I–VI) were examined for multiple anti-HIV specificities. Gp41 (but not gp120) Env immunoglobulin (Ig)A Abs were frequently elicited in both plasma and mucosal fluids within the first weeks of transmission. However, shortly after induction, these initial mucosal gp41 Env IgA Abs rapidly declined with a t1/2 of ∼2.7 days. B-cell-activating factor belonging to the TNF family (BAFF) was elevated immediately preceding the appearance of gp41 Abs, likely contributing to an initial T-independent Ab response. HIV-1 transmission frequently elicits mucosal HIV-1 envelope-specific IgA responses targeted to gp41 that have a short half-life.

B-Cell-Activating Factor Affects the Occurrence of Thyroid Autoimmunity in Chronic Hepatitis C Patients Treated with Interferon Alpha

Chronic hepatitis C (CHC) patients frequently suffer from thyroid disorders during interferon therapy. However, the mechanism remains unclear. In this study, we investigated the association between serum B-cell-activating factor belonging to the TNF family (BAFF) levels and the presence of antithyroid peroxidase antibody (anti-TPO) in CHC patients treated with pegylated interferon alpha and ribavirin combination therapy. Six months after the therapy, anti-TPO antibody was detected in 10 (males, 1; females, 9) of 50 patients. The mean age of these patients was higher than that of the anti-TPO-negative patients (61 yr versus 55 yr). Before treatment, the serum BAFF levels of the anti-TPO-positive patients were higher than those of the anti-TPO-negative patients. After starting therapy, the serum BAFF levels of both the anti-TPO-positive and -negative patient groups were elevated. Our findings suggest that the serum BAFF concentration before therapy can predict the risk of thyroid autoimmunity in elderly female patients with CHC.

Selective killing of Burkitt's lymphoma cells by mBAFF-targeted delivery of PinX1

Increased expression of BAFF (B cell-activating factor belonging to the TNF family) and its receptors has been identified in numerous B-cell malignancies. A soluble human BAFF mutant (mBAFF), binding to BAFF receptors but failing to activate B-lymphocyte proliferation, may function as a competitive inhibitor of BAFF and may serve as a novel ligand for targeted therapy of BAFF receptor-positive malignancies. Pin2/TRF1-interacting protein X1 (PinX1), a nucleolar protein, potently inhibits telomerase activity and affects tumorigenicity. In this study, we generated novel recombinant proteins containing mBAFF, a polyarginine tract 9R and PinX1 (or its C/N terminal), to target lymphoma cells. The fusion proteins PinX1/C–G4S–9R–G4S–mBAFF and PinX1/C–9R–mBAFF specifically bind and internalize into BAFF receptor-positive cells, and subsequently induce growth inhibition and apoptosis. The selective cytotoxicity of the fusion proteins is a BAFF receptor-mediated process and depends on mBAFF, PinX1/C and 9R. Moreover, the fusion proteins specifically kill BAFF receptor-expressing Burkitt's lymphoma (BL) cells by inhibiting telomerase activity and the consequent shortening of telomeres. Therapeutic experiments using PinX1C–G4S–9R–G4S–mBAFF in severe combined immunodeficient (SCID) mice implanted with Raji cells showed significantly prolonged survival times, indicating the in vivo antitumor activity of the fusion protein. These results suggest the potential of PinX1/C–G4S–9R–G4S–mBAFF in targeted therapy of BL.

Serum BAFF and APRIL levels in patients with PBC

B-cell-activating factor belonging to the TNF family (BAFF) and a proliferation-inducing ligand (APRIL) are known to be involved in the occurrence of autoimmune diseases. We assessed serum levels of these cytokines in PBC patients. Serum BAFF levels were significantly higher in PBC patients than in healthy controls (1253.9+/-741.4 vs. 722.8+/-199.2 pg/ml; p<0.0001) and HCV-infected patients (1253.9+/-741.4 vs. 871.0+/-251.1 pg/ml; p=0.015). Whereas changes in serum APRIL levels were not significant among these groups, there was a significant correlation between BAFF and AST (R=0.278, p=0.003) or total bilirubin (R=0.363, p=0.0006) in PBC patients. Furthermore, serum BAFF levels were elevated in PBC patients with advanced interface hepatitis. Our data indicate that serum levels of BAFF and APRIL are differentially regulated and serum BAFF levels are significantly elevated in PBC patients. These findings suggest that BAFF may serve as a modulator of the clinical and/or serological manifestation in PBC patients.

BAFF and BAFF-R of peripheral blood and spleen mononuclear cells in idiopathic thrombocytopenic purpura

BAFF (B-cell activating factor belonging to the TNF family) is an essential component of B-cell homeostasis, and is required for the normal survival and development of B cells. To further explore the role of this cytokine in the pathogenesis of idiopathic thrombocytopenic purpura (ITP), BAFF/BAFF-R (one of receptors of BAFF) expression levels were determined and the correlation between the clinical parameters and the BAFF expression levels was analyzed. A total of 57 patients with ITP were enrolled and 25 age and sex-matched healthy volunteers served as controls. Serum was obtained from 41 patients with ITP and 22 healthy volunteers and was analyzed with a commercial human soluble BAFF (sBAFF) ELISA kit. BAFF and BAFF-R mRNA expression of peripheral blood (PB) (n = 42) and splenocytes (SP) (n = 8) mononuclear cells (MNC) were determined by real-time quantitative PCR. The SPMNC of normal controls came from three hereditary spherocytosis patients who underwent splenectomy. The untreated patients with ITP had higher serum BAFF levels (Median 1430 pg/ml, Range: 534–5787 pg/ml) than those of normal controls (Median 1120 pg/ml, Range: 640–2376 pg/ml, p = 0.006) and treated ITP group (Median 662 pg/ml, Range 267–1265 pg/ml, p = 0.000). On the other hand, serum BAFF levels of treated patients with ITP were lower than those of normal controls (p = 0.001). There was a weak correlation (the Pearson correlation coefficient is − 0.242) between platelet count and BAFF (p = 0.064). However, BAFF levels did not correlate with platelet associated immunoglobulin or immunoglobulin levels. Moreover, the serum BAFF levels were not statistically different between acute and chronic ITP (p = 0.841). PBMNC of ITP had higher BAFF but not BAFF-R mRNA expression than that of normal controls. BAFF mRNA expression of SPMNC had a positive correlation with BAFF-R in ITP patients but not in PBMNC of normal controls and untreated ITP patients. The BAFF-R mRNA expression of SPMNC was shown to be 15.29 times higher than that of PBMNC in ITP. BAFF might contribute to autoimmunity and disease development in ITP. However, BAFF serum level must be carefully considered as a surrogate marker of disease activity in ITP.

Deregulation of c-Myc Confers Distinct Survival Requirements for Memory B Cells, Plasma Cells, and Their Progenitors

Deregulation of the c-Myc oncogene is tightly associated with human and murine plasma cell (PC) neoplasms. Through the analysis of Ag-specific B cell responses in mice where Myc is targeted to the Igh Calpha locus, we show here that c-Myc dramatically impairs the primary and secondary Ab response. This impairment is differentiation stage specific, since germinal center B cell formation, affinity maturation, and class switch recombination were intact. Examination of PC viability revealed that c-Myc triggered apoptosis only upon final maturation when Ab is secreted and is resistant to the survival factor BAFF (B cell-activating factor belonging to the TNF family). In contrast, PC precursors (PC(pre)) that ultimately give rise to mature PCs survived normally and vigorously expanded with BAFF signaling. We further show that c-Myc also facilitates the apoptosis of memory B cells. Thus, Calpha-Myc controls both cellular arms of long-lived B cell immunity than previously anticipated. Only when deregulation of c-Myc was combined with enforced Bcl-x(L) expression were mature PCs able to survive in response to BAFF. These data indicate that the survival requirements for tumor-susceptible PC(pre) and PCs are distinct and that tumor progression likely develops as PC(pre) transition to functional PCs when apoptotic pathways such as members of the Bcl-2 family are disabled.

Global T Cell Dysregulation in Non-Autoimmune-Prone Mice Promotes Rapid Development of BAFF-Independent, Systemic Lupus Erythematosus-Like Autoimmunity

In otherwise non-autoimmune-prone C57BL/6 (B6) mice rendered genetically deficient in CD152 (CTLA-4), polyclonal hypergammaglobulinemia with increased levels of systemic lupus erythematosus (SLE)-associated IgG autoantibodies, glomerular IgG and C3 deposition, and interstitial nephritis all developed by 3-5 wk of age. Remarkably, superimposing genetic deficiency of BAFF (B cell-activating factor belonging to the TNF family) onto CD152 deficiency did not substantially attenuate humoral autoimmunity and immunopathology in these mice, despite the resulting marked reduction in B-lineage cells. Although superimposing a BAFF transgene (resulting in constitutive BAFF overexpression) onto CD152-deficient mice did lead to increases in B-lineage cells and serum levels of certain SLE-associated IgG autoantibodies, renal immunopathology remained largely unaffected. Taken together, these results demonstrate that global T cell dysregulation, even in an otherwise non-autoimmune-prone host, can promote systemic humoral autoimmunity and immunopathology in a BAFF-independent manner. Moreover, supraphysiologic expression of BAFF in the setting of ongoing autoimmunity does not necessarily lead to greater immunopathology. These findings may help explain the limited clinical efficacy appreciated to date of BAFF antagonists in human SLE.

Expression of BAFF and BAFF‐R in the synovial tissue of patients with rheumatoid arthritis

Objective: The elevated expression of B‐cell‐activating factor belonging to the TNF family (BAFF) is associated with systemic autoimmune disease, including rheumatoid arthritis (RA). The present study was undertaken to determine the distribution of BAFF and its receptor BAFF‐R in the cells residing in the rheumatoid synovium.Methods: The expression of BAFF and BAFF‐R in synovial tissues obtained from 12 RA patients was examined by immunohistochemistry and flow cytometry. The mRNA expression of these molecules was determined by reverse transcriptase polymerase chain reaction (RT‐PCR). Soluble BAFF levels were measured with an enzyme‐linked immunosorbent assay (ELISA). Fibroblast‐like synoviocytes (FLS) purified from the RA (RA‐FLS) were co‐cultured with peripheral B cells. The degree of apoptosis in the B cells was measured to assess the effects on the viability of the B cells.Results: The RA synovium showed focal or diffuse infiltration of mononuclear cells (MNCs), and one specimen showed germinal centre (GC)‐like structures. Synovial sublining cells, but not lining cells, expressed BAFF. These sublining cells were negative for BAFF‐R. BAFF and BAFF‐R were expressed in B and T cells extracted from the RA synovium. Notably, RA‐FLS spontaneously expressed cytoplasmic BAFF after 4–6 passages; however, they did not express BAFF or BAFF‐R on their cell surface. RA‐FLS could support the survival of B cells by preventing their apoptosis, but its effect on B cells might not be BAFF dependent.Conclusions: BAFF and BAFF‐R are widely expressed in the RA synovium. The cells residing in the RA synovium might affect each other through BAFF.

Regulation of B-cell survival by BAFF-dependent PKCdelta-mediated nuclear signalling.

Approximately 65% of B cells generated in human bone marrow are potentially harmful autoreactive B cells. Most of these cells are clonally deleted in the bone marrow, while those autoreactive B cells that escape to the periphery are anergized or perish before becoming mature B cells. Escape of self-reactive B cells from tolerance permits production of pathogenic auto-antibodies; recent studies suggest that extended B lymphocyte survival is a cause of autoimmune disease in mice and humans. Here we report a mechanism for the regulation of peripheral B-cell survival by serine/threonine protein kinase Cdelta (PKCdelta): spontaneous death of resting B cells is regulated by nuclear localization of PKCdelta that contributes to phosphorylation of histone H2B at serine 14 (S14-H2B). We show that treatment of B cells with the potent B-cell survival factor BAFF ('B-cell-activating factor belonging to the TNF family') prevents nuclear accumulation of PKCdelta. Our data suggest the existence of a previously unknown BAFF-induced and PKCdelta-mediated nuclear signalling pathway which regulates B-cell survival.

BAFF: B cell survival factor and emerging therapeutic target for autoimmune disorders

The prevailing treatment strategies for autoimmune disorders employ global immunosuppressants that have harmful side effects with long-term use. A new vision for drug development relies on the generation of therapeutics that have specific and narrow targets, such as pathogenic cell populations. The cellular processes that initiate and maintain B cell dysregulation are not well understood and autoimmune disease results, in part, from the survival and activation of self-reactive B cells. Such B cells produce tissue-damaging pathogenic autoantibodies. BAFF (B cell-activating factor belonging to the TNF family), a member of the TNF family of ligands, may play a role in B cell-mediated diseases. BAFF is a survival factor for peripheral B cells. When BAFF is overexpressed in mice, B cell number and immunoglobulin production is increased and an autoimmune-like phenotype is observed. Mouse models of lupus-nephritis have been shown to exhibit increased serum BAFF levels correlating with disease severity, and many autoimmune patients were found to have higher levels of circulating BAFF than healthy volunteers. Thus, modulating the level and activity of BAFF in these patients may alleviate symptoms associated with their disease. Several potential therapeutic inhibitors targeting BAFF are under investigation, including an anti-BAFF antibody and receptor–Fc fusion proteins.